At a Glance
- Apple scab incidence is increasing in some Okanagan orchards and is appearing more frequently at the packinghouse.
- Scab can show as visible lesions on fruit or leaves, or later as pinpoint scab in storage.
- Fruit affected by scab is unmarketable, leading to significant crop losses.
- The disease overwinters in leaf litter and infections can occur from green tip through bloom and fruitlet stages.
- The BC DAS Apple Scab model uses local weather data to identify infection periods and support spray decisions.
Why Is Apple Scab a Problem?
Apple scab, caused by the fungus Venturia inaequalis, has been increasing in incidence in a number of orchards in the Okanagan region, with higher levels being detected at the packinghouse. Scab can appear as the more traditional lesions or “scabs” on fruit and leaves during the growing season, or it may develop later in storage as pinpoint scab.
Because apples affected by scab are unmarketable, even small levels of infection can result in significant losses. Understanding how scab develops and how to manage infection risk is therefore critical to protecting crop quality and market access.
Where Does Scab Come From?
Apple scab overwinters in infected leaf litter on the orchard floor in the form of spores (ascospores). When moisture is present, such as during rainfall or irrigation events, these spores can be released from the orchard floor and carried onto developing green tissue.
As a result, growers should be aware of potential scab infection periods from green tip, through bloom, and into the fruitlet stage, when susceptible tissue is present and conditions are favourable for infection.
How the BC DAS System Helps
The BC DAS system helps keep growers informed about scab infection periods based on their specific geographic location. After a grower enters the green tip date for an orchard block, the system incorporates up-to-date data from nearby weather stations across the valley.
By tracking factors such as average temperature, cumulative wetness hours, and the short-term forecast, BC DAS identifies when conditions are favourable for scab infection. The system provides alerts to notify growers of past, current, or upcoming infection periods, supporting timely management decisions.
Tools to Support Scab Management
In addition to infection alerts, the BC DAS Scab model includes access to control measures through the DAS Spray Guide. When a scab infection alert occurs, growers can view spray options for:
- Protectant products (before an infection)
- Eradicant products (after an infection)
The Spray Guide also allows growers to filter products that are registered for conventional or organic use. By following the BC DAS Apple Scab model, growers have access to timely information and up-to-date tools to help reduce the risk of scab infections compromising their crop.
Learn More (Video)
Interested in learning more? Check out the BC DAS video on the Apple Scab Model on YouTube to see how field knowledge connects with the online system.